This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Osteoarthritis (OA) is a common and painful condition with a multi-factorial etiology of the musculoskeletal system affecting more than 50% of the U.S. population over 65. Degeneration of the articular cartilage tissue, which is believed to be a primary factor in the development of OA, is a slow process and typically takes decades to have full thickness loss, but can be significantly accelerated due to trauma or surgical procedures. Dunkin-Hartley guinea pigs have been shown to develop OA with the earliest stage of detection manifesting as early as three to four months of age. Therefore, the Dunkin-Hartley guinea pig model provides a practical system for the longitudinal studies of the progression of OA. Quantitative assessment of glycosaminoglycan (GAG) molecules can assist with assessment and treatment of cartilage degradation. Chemical exchange between labile protein protons and bulk water can make MRI sensitive to information about the concentrations and environments of endogenous proteins. Chemical Exchange Saturation Transfer (CEST), a technique which uses the attenuation of bulk water magnetization through magnetization exchange with saturated labile protons, has become a popular method for measurement of metabolites with exchangeable protons. GAG contains amino groups (-NH2) and hydroxyl groups ([unreadable]OH) that exchange protons with bulk water that can be exploited for CEST. This offers a potential endogenous marker for the determination of GAG content in tissue. Hence, CEST may provide a sensitive and specific marker for GAG assessment. Therefore, the aim of this study is to develop a CEST protocol to accurately quantify biochemical properties of the articular cartilage on guinea pig cartilage at 9.4 T.